A carboxylic acid containing 40% carbon and 6.7% hydrogen is …

To solve, we write down the general formula of carboxylic acid: СnH2nO2.
The molar mass of the carboxylic acid is 100 w.h. = 100%, hence, W (O) = 100 – (40% + 6.7%) = 53.3%;
Let’s determine the number of moles of carbon, hydrogen, oxygen:
Y (C) = m / M = 40/12 = 3.33 mol;
Y (H) = 6.7 / 1 = 6.71 mol;
Y (O) = 53.33 / 16 = 3.33 mol;
Ratio: C: H: O = 3.33: 6.7: 3.33 = 1: 2: 1;
The simplest formula: CH2O;
Let’s make calculations using the general formula of carboxylic acid:
M (CnH2n + 1COOH) = 100 g / mol;
12n + 2n + 1 + 12 + 16 * 2 + 1 = 100;
12n = 100 – 48;
12n = 52;
n = 4;
Molecular formula: C3H7COOH;
Answer: the formula is С3Н7СООН – butanoic acid.